Improvement in processes for pulping paper-stock



UNITED STATES PATENT OFFICE.

HECTOR J. LAHOUSSE, OF PRAGUE, BOHEMIA, ASSIGNORTO HIMSELF AND HOWARDLOOKWOOD, OF NEW YORK, N. Y.

IMPROVEMENT IN PROCESSES FOR PULPING PAPER-STOCK.

Specification forming part of Letters Patent No. 153,775, dated August4, 1874 ap lication filed April 4, 1874.

T 0 all whom it may concern:

Be it known that I, HECTOR J. LAHOUSSE, of Prague, in-Bohemia, haveinvented a new and Improved Process for Pulping Paper Stock, of whichthe following is a specification:

The object of my invention is to reduce the knots and joints of strawand similar fibrous materials, after being properly boiled to a uniformpulp, more effectually and uniformly than it is now done in the commonpulpingengine, enabling the bleaching-liquor to penetrate and come incontact with all the fiber of the stock; also, to regulate and controlmore effectually the temperature of the stock which is being reduced,and the bleachin g-h'quor to a proper temperature for bleach- Myinvention consists in subjecting the pulp and the bleaching-liquor tothe action of a grinding-mill, in lieu of the ordinary beatingengine,for reducing the knots and joints and for raising the temperature to therequired point, whereby certain advantages are obtained, as hereinafterdescribed.

The straw being properly boiled and all the alkali washed out, alsotreated in the wet machine, or not, according to circumstances, alsotreated in the paper engine or mixer, and thoroughly saturated with ableaching-liquor of proper strength, and also agitated in a stuff-chest,I propose to take it from the latter by a pump or other means, andconduct it to a grinding-mill of ordinary or any approved construction,such as used for grinding grain, and pass it through to crush the knotsand joints, and raise the temperature by the friction of the stones.

The mill performs a double office: First, by reducing the straw orsimilar fibrous materials, especially the knots and joints, to a fineand uniform pulp, enabling the bleachingliquor to penetrate and come incontact with all the fibers of the stock, and also to act uniformly uponit, which has never successfully been done in any beating-engine atpresent in use; secondly, the friction created by the faces of thestones running together, in order to reduce the stock to a fine anduniform fiber,

at the same time raises the temperature of the stock andbleaching-liquor to between 85 and 110 Fahrenheit.

Thus it will be seen that while the stock is being reduced to a finefiber, and becomes thoroughly incorporated with the liquor, thetemperature is raised at the same time to the proper point forbleaching. The chlorine gas contained in the bleaching-liquor is setfree and acts most effectually upon the stock at about 96 Fahrenheit.

From the mill the stock can be conducted to an air-blast, so that it maybe cooled, and to complete the bleaching operation by being brought incontact with cool air. Instead of this, it may be run into a tub theshape of a paper or beating engine, and agitated by a paddle-wheel forseveral hours, bringing all the stock in contact with air and light,which would produce the same effect.

There are other points in the manufacture of pulp from straw and similarfibrous materials in which this method of pulping and bleaching hasdecided advantages over the present processes.

The stock need not be as much subdued preparatory to the treatment inthe grinding mill, thereby saving chemicals and producing a larger percent., and a very much stronger fiber.

In the present way of bleaching, the stock has to be over subdued ortreated in order to get the knots and joints soft, which very severetreatment, in great part, destroys the texture and strength of thefibers and reduces the percentage of yield.

If the knots and joints are not soft, there is no means of reducing themto a uniform fiber with any of the present systems. An ordinarypaper-engine would chop the knots and joints into small lumps, in whichcondition they would not take the bleach, and consequently will show asyellow spots in the paper.

It has been determined that chlorine gas will impart its bleachingqualities to the stock troducing a small jet of steam into the stockwhile undergoing the bleaching process. Steam from one pound to sixtypounds pressure would be from 212 to 300 Fahrenheit. A jet of steamintroduced into the stock at such a temperature, say for two hours-thenecessary time to bring the whole mass up to the proper pointwould comein contact with a large per cent. of the stock, and produce bad results.

At no time is any part of the stock, while passing through my pulpingand bleaching mill, exposed to a higher temperature than the maximum forgood and proper bleaching.

The pulping and bleaching portion of my process is carried on about asfollows: Atter the straw is boiled under pressure, in a caustic alkaliin a close vessel, it is washed in the usual manner to get rid of thespent liquor and coloring matter. It is then mixed with a solution ofbleaching-liquor (chlorate of lime in solution) in a paper-engine orother suitable apparatus. From this it is run through the stones for thepurposeoi' reducing the stock to a uniform fiber, which enables it tobetter absorb the bleaching-liquor; also, while passing through thestones, is at the same time produced the additional and importanteii'ect of raising the temperature to the proper point for goodbleaching, say from 85 to 110 Fahrenheit, which produces the bestresults.

The temperature is regulated and maintained at the desired point in thefollowing manner: In order to reduce the stock to a uniform fiber, thestones are set in close proximity to each other, and one of them is runat the rate of two hundred (200) revolutions per minute. Through thismill is run a stream of pulp about equal to fifty pounds per hour of drypaper-stock, the friction raising the temperature. If the stock gets toohot, increase the flow of pulp to the mill; if too cool, decrease it. Ifit is necessary to increase the quantity of pulp which is passingthrough the mill, and at the same time keep up the proper temperature,increase the number of revolutions per minute to two hundred and fifty(250) or even more.

For the following reasons I consider that this process possesses markedadvantages over all other systems known to me: First, chemicals aresaved and the product of pulp from each ton of straw increased, since itis not necessary to subdue the straw until all the joints are soft, asthe stones brush them out to a fiber; second, the friction of the stonesproduces the combined effect of raising the temperature to the properpoint for setting free the chlorine gas, and at the same time reducingthe stock to a fine fiber, in which condition it is most easily actedupon by the gas.

Having thus described my invention, I claim as new and desire to secureby Letters Paten t-- The method of treating paper-stock subsequent tothe boiling process, by first cooling and mixing it with thebleaching-liquors, and, secondly, grinding the pulp together with thebleaching liquors, to reduce the knots and joints, and to utilize thefriction of the mill to heat the pulp to the proper bleachingtemperature, substantially as specified.

The above specification of my invention signed by me this sixth day ofMarch, 1874.

HECTOR JOSEPH LAHOUSSE.

Witnesses:

.S. E. nu Vnconv,

Prof. OSCAR COCORDA.

